Punnett Squares Make Predictions If I have a

Punnett Squares

Make Predictions! If I have a black rabbit and a white rabbit, and they mate, what color do you think their offspring will be? + = ?

Punnett Square Why? Way of predicting the likelihood (probability) of offspring carrying certain genetic traits!

What do we need to know? 1. Genotype of parents 2. Which allele is dominant

Purebred = Homozygous Purebred: Both alleles are for the same trait Example: FF

Hybrid = Heterozygous Hybrid = The alleles are mixed; they are for different traits Example: Ff

Quick Check: Homozygous = stand up, Heterozygous = sit down BB Homozygous Bb Heterozygous bb Homozygous b. B Heterozygous

Remember, capital letters are DOMINANT!

Let’s try another Punnett Square! Hair Color in Humans B = brown = dominant b = blonde = recessive Let’s say Kevin Federline and Britney Spears are having a baby…

KFed is heterozygous for brown hair, so…. And Britney is homogenous for blonde hair, so…. Her genotype is His genotype is bb Bb B b b b Bb Bb bb bb

Genotype Bb bb b b B Bb Bb b bb bb Ratio 2/4 Percentage Phenotype Ratio Percentage 50% Brown Hair 2/4 50% Blonde Hair 2/4 50% The likelihood that an offspring will have Brown Hair is _______. The probability that an offspring will have Blonde Hair is ______.

***Important*** Probability is the likelihood something will happen, or the chance that something will happen. If there is a 25% chance that your kids will have blue eyes, it does not mean that if you have 4 kids one of them is definitely going to have blue eyes!

Widow’s Peak a recessive gene W = Normal Hairline w = Widow’s Peak

Let’s say you have two parents who are heterozygous for the gene… What are their genotypes? Ww and Ww 1. What are the chances that their offspring will have a widow’s peak? 2. What are the chances that their offspring will not have a widow’s peak but will carry an allele for a widow’s peak? 3. What are the chances that their offspring will not have a widow’s peak and will not carry a gene for a widow’s peak?

Let’s see what happens if the parents have the following genotypes: Ww and ww 1. What are the chances that their offspring will have a widow’s peak? 2. What are the chances that their offspring will not have a widow’s peak but will carry an allele for a widow’s peak? 3. What are the chances that their offspring will not have a widow’s peak and will not carry a gene for a widow’s peak?